Thanks guys for the great info! I'll give your suggestions a try. I still am not sure of all the lingo yet. For instance , setting your high speed needle...is that in fact running full throttle? Does anybody use a tach when setting your mixture? When I lean out a Cessna 172, I run it up to 1700 RPM and lean out until I get an increase in RPM, followed by a drop. Then I enrichen back just short of the peak RPM. Seems like your method is similar, Campy? I think I will download the OS manual and also try to find articles in the magazines concerning proper tuning. Plus I'll pick up a couple of OS 8 glow plugs. Thanks again guys for helping this newbie out! Just another quick question...what does the different percentages of nitro do for you and do I need to be concerned with overheating with too high of a nitro concentrate? I've been running 15% but my new jug is 25%. Any problems with this for a .40 engine? Thanks!